The invention relates to a current lead for connecting a superconducting load system, in particular, a magnet coil, to a current feed point that is at a higher temperature than the load system, comprising                a flat, elongated carrier and        a plurality of mechanical and electrically parallel high-temperature superconductors (HTSC),wherein the HTSCs are disposed side by side on the carrier.        
The generic prior art is disclosed in DE 10 2005 058 029 A1.
Superconducting load systems are deployed wherever (usually strong) electrical currents must flow with low electrical resistance. One important superconducting load system is superconducting magnet coils, which are used to produce strong magnetic fields, for example, for NMR spectrometers or MRI tomographs. The superconducting load system must be kept at a cryogenic temperature for operation so that the superconducting material in the load system can be kept below its critical temperature Tc. The superconducting load system must be refrigerated with cryocoolers for this purpose; the necessary cooling power or the energy required to provide the cooling power is a considerable cost factor.
Electric current is fed into the superconducting load system during start-up or also during operation. For this purpose, current leads are used. Current leads should therefore provide a current path with good electrical conductivity. Current leads connect a current feed point to the superconducting load system at the cryogenic temperature.
Because the current sources (such as the local power supply network) usually provide their connections at room temperature, the current lead always provides a thermal conduction path to the superconducting load. The associated heat input increases the cooling power requirement of the superconducting load.
Normally, graduated cooling is provided for the power supply. The first end of the current lead, nearest to the current feed point, or the corresponding first connection element is kept at a medium low temperature (for example, 50 to 90 K) by a first cryocooler or a first stage of a cryocooler. The second end of the current lead near to the superconducting load or a corresponding second connection element is kept at the temperature intended for the superconducting load (usually 1 to 30 K) by a second cryocooler or a second stage of a cryocooler. This graduated cooling already considerably reduces the cooling power requirement.
The current lead disclosed in DE 10 2005 058 029 A1 is an FRP (fiberglass reinforced plastic) carrier comprising two identical plates, between which strip-shaped, mutually parallel high-temperature superconductors (HTSC) are disposed. The HTSCs extend in the longitudinal direction of the FRP carrier. The ends of the HTSCs are connected electrically-conductively each with a connection element. The strip-shaped HTSCs each comprise a normally conducting current path.
The disadvantage of this current lead is the relatively low superconducting current capacity relative to the dimensions and, furthermore, if the superconductivity is no longer ensured in the HTSC (quench), the emergency conducting properties are weak.
It is the object of this invention to provide an HTSC current lead with a high current capacity and low thermal conductivity that provides improved emergency conduction properties in case of failure of the superconductivity in the HTSC.